Hi everyone Some more information on the New Zealand DRM tests using the AM Network/Southern Star 657 MW transmitter at Titahi Bay over the past 3 days.
Chris Mackerell here in Wellington has very accurately recorded a lot of what's been going on. In this region, every MW station has a usable bandwidth of 18kHz, so for 657, it means they can (within certain parameters) broadcast a signal that extends from 648-666. DRM is about 'fitting in' a number of additional signals depending on how the 18kHz is carved up for different standards such as data, voice only, and music, and whether you want mono, partial stereo or full stereo and whether you wish to simply simulcast on analog/DRM. The tests have juggled around different uses such as 657 in analog, and 661.5 in DRM (shown on most DRM receivers as 662), using 657 in analog and 652.5 (briefly) in DRM, and, both yesterday and today, a world first with the DRM signal extending the full 18kHz bandwidth to deliver full stereo. The DRM power used yesterday was 1.25kW and at times this afternoon was powered at 10kW DRM whilst mobile testing took place of signal degradation at a distance from Titahi Bay in the Wairarapa, over the Rimutakas hill range about 40km north of Wellington, and about 30km from Titahi Bay. The signal clearly dropped out at times on the Rimutaka Hill Road, gaining as much as 10db when at the summit, in fact, very similar to FM reception. Yesterday, the signals were tested for reception within the 'concrete canyon' of central Wellington's highrise building district where they performed well. The program feeds have been mostly Southern Star, although yesterday, output from a series of CD's in Radio NZ House was carried by a Telecom link to the transmitter and covered a range of musical genres as well as voice. With direct links to the transmitter and several professional DRM receivers, it was possible to hear the original CD quality in the room, AM quality (analog) and DRM quality during simulcasting tests and make instant quality comparisons. This afternoon, the full DRM signal relayed RNZ's Concert FM for a short while, and then EZL music was inserted at the transmitter site. The DRM tests are allowing observations relating to such things as robustness of the signal, maintaining same coverage as AM but using a lower DRM power consumption at the transmitter, quality of bandwidth used for DRM such as 4.5, 9 and 18 kHz, effect on the 657 analog reception when in simulcast mode, effect on 648 and 666 kHz stations and a heap of other stuff. The effect of running 10kW DRM power is a bit like having a 200kW analog signal being broadcast, so not only do you get full stereo, but your coverage area remains much the same as that achieved by the original analog signal. Well, that's the theory. I'll be presenting a radio heritage documentary on the DRM tests and DRM in the Pacific over RNZI in June, with major excerpts from the symposium, in particular speakers Andy Giefer from Deutsche Welle, Lindsay Cornell (BBCWS) and a number of other speakers including the ABU. The Radio Heritage Foundation was kindly hosted by RNZI and RNZ to ensure that the heritage aspects of the event were recorded, as the shift to the digital era in radio broadcasting is in danger of under reporting and preservation worldwide. In this case, the full 18kHz bandwidth DRM transmissions are a world first, as in Europe they're restricted to 9kHz. Pacific radio heritage in the making. There are many issues I'll attempt to cover in the documentary, and in comments at www.radioheritage.net in the coming weeks. As a MW DXer, I'm also interested in seeing how the DRM 'hiss' can be reduced or eliminated, and the imperative, in my view, will probably come from adjoining and co-channel stations who see their coverage areas being threatened and a commercial cost as a result. There seems no doubt that day/night switching will be a key issue. One option is to reduce the number of DRM channels at night (say from 2 or 3 to just 1)and reduce DRM power at night because of skywave issues. The quality of receivers also impacts on 'hiss', because most (estimated 95%) of tuners have narrow bandwidth sensitivity only, with mainly older valve sets having the greater bandwidth we DXers demand. >From discussions with a variety of broadcasters, it also became apparent that the value of 'on the spot' monitoring by 'ordinary listeners' of signals and DRM interference, is going to take on more importance. Yes folks, DX reports will become wanted again by the technical people. In fact, leaving DRM aside, reception reports for specific tests and/or frequencies and 'comparison' rating of reception of a number of AM transmitters in a defined area will clearly be welcomed. It will be 'DXing to order', but offers some interesting opportunities for MW DX around the Pacific. Watch the usual chat groups and www.radioheritage.net for more details in coming months. Warm regards David Ricquish www.radioheritage.net ---[Start Commercial]--------------------- World Radio TV Handbook 2005 is coming out. Preorder yours and support open communications for DXers: http://www.amazon.com/exec/obidos/ASIN/0823077942/hardcoredxcom ---[End Commercial]----------------------- ________________________________________ Hard-Core-DX mailing list [email protected] http://dallas.hard-core-dx.com/mailman/listinfo/hard-core-dx http://www.hard-core-dx.com/ _______________________________________________ THE INFORMATION IN THIS ARTICLE IS FREE. 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